OTTAWA (AFP) - The best that NATO forces can hope for in Afghanistan is to "push back the insurgency," which can never be wholly defeated, Canadian Prime Minister Stephen Harper said Friday. "We have to define what victory means in Afghanistan, and I don't think victory realistically can mean international or Western forces under NATO eliminating every last vestige of the insurgency," Harper told reporters. "I just don't think that's realistic, if you look at the history of Afghanistan, if you look at the history of the insurgency, the porous border (with Pakistan). "But I think what is realistic is we would considerably push back the insurgency," he said, to facilitate aid and development, as well as the handover of security responsibilities to Afghan forces. The comments followed Harper's interview with CNN on March 1, in which he claimed the United States and its allies would never defeat the insurgency.